Method of fabricating color filter

ABSTRACT

A method of fabricating a color filter is provided. First, a substrate having a light shielding layer formed thereon is provided, wherein the light shielding layer is adopted for defining a plurality of sub-pixel regions on the substrate. Next, a hydrophobic layer is formed on the light shielding layer by stencil printing, or a surface silylation treatment is carried out to clean the light shielding layer by inkjet printing. Next, a color filter layer is formed in the sub-pixel regions. Thus, fabrication method of the present invention is capable of reducing the possibility of intermixing the color ink between adjacent sub-pixel regions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a method of fabricating acolor filter. More particularly, the present invention relates to amethod of fabricating a color filter, wherein the possibility ofintermixing between the color inks in adjacent sub-pixel regions can besubstantially reduced.

2. Description of Related Art

As the development of the performance of computer, internet, andmultimedia technology, the transformation of image information hasgradually progressed from analog information to digital information. Inrecent years, the size and weight of many electronic device hasgradually reduced to produce thinner and lighter electronic products. Asto a display device, although the conventional cathode ray tube (CRT)display is widely used, however, it has the disadvantages of large size,high radiation, heavy weight and high power consumption. Therefore, theflat panel display (FPD), which has the advantages of being thinner,flatter, lighter, low or radiation free, and low power consumption, hasgradually become the mainstream of display devices. The flat paneldisplay (FPD) includes, for example, liquid crystal display (LCD),organic light emitting display (OLED) or plasma display panel (PDP).

A conventional liquid crystal display (LCD) consists mainly of a thinfilm transistor (TFT) array, a color filter, and a liquid crystal layerdisposed between the thin film transistor array and the color filter.The color display of the liquid crystal display is generally performedby color filters. The color filter is generally constructed over atransparent glass substrate. The color filter generally comprises ablack matrix and a color filter layer comprising, for example, redfilter units, green filter units and blue filter units arrangedcorresponding to each sub-pixel, wherein the black matrix is adopted forshield light.

A fabrication method for forming a color filter layer by inkjet printinghas been developed recently. According to this conventional fabricationmethod, first, a black matrix is formed on a substrate to define aplurality of sub-pixel regions. An inkjet printing process is thenperformed to inject color ink (red, green, or blue) into the sub-pixelregions defined by the black matrix. Next, a thermal baking process maybe performed to solidify the color ink.

The above conventional fabrication method, however, has someshortcomings, such as, during the injection of color ink into thesub-pixel regions between patterns of the black matrix, the level ofcolor ink in each of sub-pixel areas is often higher than the surface ofthe black matrix since the volume of the color ink injected is usually alittle larger than that defined by the sub-pixel areas. Therefore, theproblem of intermixing of the color inks in adjacent sub-pixel regionsmay occur if the inkjet printing process is not properly controlled.

In order to resolve the above problem, a hydrophobic film is formed onthe black matrix before forming the color filtering layer using a plasmaprocess. However, instead of obtaining an expected flat hydrophobicfilm, usually a black matrix film with island structures formed thereonis obtained due to variation in the processing recipe, resulting inoverflow of color inks and intermixing color inks. Furthermore, thehazardous CF₄ gas used in the plasma process is also a grave safetyconcern.

In addition, another conventional method, disclosed in Japanese PatentPublication No. 09230127, includes coating a 25%C₈F₁₇C₂H₄—Si—(OCH₃)₃/methanol solution over the substrate and etchingusing a solution comprising 1% Buffer Fluoric acid (50% HF:40% NH4F).Thereafter, a color filter layer is formed in the sub-pixel regions.Since the 25% C₈F₁₇C₂H₄—Si—(OCH₃)₃/methanol solution is coated over theentire substrate, the surface of the substrate in the sub-pixel regionsmay still have hydrophobic property even though a cleaning process isbeing performed thereafter, and the problem of intermixing of the colorinks in adjacent sub-pixel regions still occurs. Besides, the entireprocess time is longer than 8 hours, and the use of HF acid is of agrave safety concern.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a method of fabricating acolor filter, in which the possibility of intermixing between the colorinks in adjacent sub-pixel regions can be substantially reduced.

According to an embodiment of the present invention, first, a substratehaving a light shielding layer formed thereon is provided, wherein thelight shielding layer defines a plurality of sub-pixel regions on thesubstrate. Next, a hydrophobic layer is formed on the light shieldinglayer by stencil printing. Next, a color filter layer is formed in thesub-pixel regions.

According to an embodiment of the present invention, the stencilprinting process mentioned above comprises a step of providing a stencilover the substrate for covering the sub-pixel regions such that thelight shielding layer is exposed. Next, a liquid-state hydrophobicmaterial is filled onto the exposed light shielding layer. Next, theliquid-state hydrophobic material is solidified to form the hydrophobiclayer. Thereafter, the stencil is removed from the substrate.

According to an embodiment of the present invention, the hydrophobiclayer mentioned above comprises Paraffin.

According to an embodiment of the present invention, the hydrophobiclayer is removed after the step of forming the color filter layer.

According to an embodiment of the present invention, the hydrophobiclayer mentioned above can be removed by treating, for example, with asolution comprising ether.

According to an embodiment of the present invention, the color filterlayer is formed by performing an inkjet printing process or aphotolithography process.

According to an embodiment of the present invention, the light shieldinglayer may be a black matrix. Wherein, the material constituting theblack matrix is, for example, epoxy resin.

The method of fabricating a color filter, according to anotherembodiment of the present invention, comprises providing a substratehaving a light shielding layer formed thereon, wherein the lightshielding layer defines a plurality of sub-pixel regions on thesubstrate. Next, a surface silylation treatment is performed on thelight shielding layer by inkjet printing. Next, a color filter layer isformed in the sub-pixel regions.

According to an embodiment of the present invention, the light shieldinglayer may be a black matrix. Wherein, the material constituting theblack matrix is, for example, epoxy resin.

According to an embodiment of the present invention, the surfacesilylation treatment comprises coating a silylate material havingformula, 2X—Si—2Y. Wherein, X is a halogen atom, and Y is a hydrophobicgroup. For example, the silylate material comprisesDimethyldichlorosilane (DMDCS).

According to an embodiment of the present invention, a cleaning processis performed for cleaning the light shielding layer after the step ofperforming the surface silylation treatment but before the step offorming the color filter layer.

According to an embodiment of the present invention, the cleaningprocess mentioned above is accomplished using a solution, for example,comprising methanol.

According to an embodiment of the present invention, the color filterlayer is formed by performing an inkjet printing process or aphotolithography process.

Since a hydrophobic layer formed by stencil printing or a surfacesilylation treatment performed by inkjet printing for cleaning the lightshielding layer before forming the color filter layer, the possibilityof intermixing between the color inks in adjacent sub-pixel regions canbe effectively reduced. Thus, the process yield can be effectivelypromoted.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1A through 1G are schematic cross-sectional views illustrating aprocess of fabricating a color filter according to an embodiment of thepresent invention.

FIG. 2A through 2D are schematic cross-sectional views showing a processof fabricating a color filter according to another embodiment of thepresent invention.

FIG. 3 illustrates the reaction between the dimethyldichlorosilane andthe black matrix of epoxy resin during the silylation reaction.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

FIG. 1A through 1G are schematic cross-sectional views illustrating aprocess of fabricating a color filter according to an embodiment of thepresent invention.

First, referring to FIG. 1A, a substrate 100 a is provided, wherein thesubstrate 100 a is, for example, a glass substrate having hightransmittance. Next, a light shielding layer, such as a black matrix110, is disposed on the substrate 100 a, wherein the black matrixdefines a plurality of sub-pixel regions 102 on the substrate 100 a.Wherein, the material constituting the black matrix 110 is, for example,epoxy resin, or some other materials with good light-shielding propertyand low reflectivity. According to an embodiment, the method for formingthe black matrix 110 includes forming a photo-sensitive resin layer (notshown) on the substrate 100 a by spin coating. Next, the photo-sensitiveresin layer is patterned by using the conventional photolithography toform the black matrix 110. The function of the black matrix 110 ismainly to effectively separate different colors of the emitted light soas to increase the purity of the displayed colors.

Next, referring to FIG. 1B through 1E, a stencil printing process isperformed to form a hydrophobic layer 120 on the black matrix 110. Asshown in FIG. 1B, a stencil 150 is disposed over the substrate 100 a forcovering the sub-pixel regions 102 such that the black matrix 110 isexposed. Next, as shown in FIG. 1C, a liquid hydrophobic material 122 isfilled onto the top surface of the black matrix 110 by using a scraper160, wherein the liquid hydrophobic material, for example, is a liquidparaffin. Thereafter, as shown in FIG. 1D, the liquid hydrophobicmaterial 122 is cooled to form the solid hydrophobic layer 120. Next, asshown in FIG. 1E, the stencil 150 is removed from the substrate 100 a,and retaining the hydrophobic layer 120 covering the black matrix 110.

Next, referring to FIG. 1F, a color filter layer 130 is formed in thesub-pixel regions 102. As shown in FIG. 1F, an inkjet printing processor a photolithography process is performed to inject color ink 132 intothe sub-pixel regions 102 defined by the black matrix 110. For example,the color ink 132 filled into the sub-pixel regions 102 includes red,green and blue ink. Thereafter, an exposing or drying process isperformed to solidify the color ink 132 and thereby form the colorfilter layer 130 in the sub-pixel regions 102. The color filter layer130, for example, comprises red filter units, green filter units andblue filter units arranged corresponding to each sub-pixel region 102.

Thereafter, referring to FIG. 1G, the hydrophobic layer 120 can beremoved by using a solution, such as ether. Subsequently, a cleaningprocess and a thermal baking process may be performed. Thus, the colorfilter 100 shown in FIG. 1G can be obtained according to theaforementioned fabricating process.

Accordingly, in the an embodiment mentioned above, a material, such asliquid paraffin having high hydrophobic property and low melting point(about 50° C. to 65° C.), is adopted to form a hydrophobic layer on theblack matrix. It should be noted that the stencil printing process isperformed for forming the hydrophobic layer, thus other regions besidethe black matrix can be protected from the hydrophobic material.Moreover, the process is much simpler and inexpensive compared to theaforementioned conventional process.

FIGS. 2A through 2D are schematic cross-sectional views showing aprocess for fabricating a color filter according to another embodimentof the present invention.

As shown in FIG. 2A, a substrate 200 a, having a light shielding layer(such as a black matrix 210) disposed thereon, is first provided,wherein the black matrix 210 is adopted for defining a plurality ofsub-pixel regions 202 on the substrate 200 a. Wherein, the materialconstituting the black matrix 210 is, for example, epoxy resin, or someother materials with good light-shielding property and low reflectivity.Because, the function and the fabrication process of the black matrix210 is similar to those described in aforementioned embodiment, andtherefore a detailed description thereof is not repeated.

Thereafter, as shown in FIG. 2B, a surface silylation treatment iscarried out to clean the surface of the black matrix 210, wherein thesilylation treatment includes inkjet printing. According to anembodiment of the present invention, the surface silylation treatmentincludes injecting a silylate material having a formula 2X—Si—2Y,wherein X is a halogen atom such as Cl, and Y is a hydrophobic groupsuch as CH3. In a preferred embodiment, the silylation treatment may becarried out using a solution 222 comprising 20% dimethyldichlorosilane(DMDCS)/Toluene. FIG. 3 illustrates the reaction between thedimethyldichlorosilane and the black matrix 210 comprised of epoxy resinduring the silylation reaction. As shown in FIG. 3, the —Cl ofdimethyldichlorosilane reacts with the —OH of Epoxy resin to form ahydrophobic structure having —O—Si—CH₃ bonding on the surface of theblack matrix 210.

Next, as shown in FIG. 2C, a cleaning process may be carried out using acleaning solution 224 comprising methanol, since methanol can replaceunbonded —Cl of the dimethyldichlorosilane with —CH3. Thereafter, theresidual cleaning solution 224 can be removed by an air knife (notshown).

Next, as shown in FIG. 2D, a color filter layer 230 is formed in thesub-pixel regions 202 by an inkjet printing process or aphotolithography process. For example, the color ink 232 includes red,green and blue ink. Next, a thermal baking process is performed tosolidify the color ink 232 to form the color filter layer 230 in thesub-pixel regions 202.

Accordingly, in the preferred embodiment mentioned above, a silylationtreatment is carried out on the black matrix by inkjet printing tomodify the property of the black matrix. Since the silylation treatmentis selectively carried out by inkjet printing only cleaning the surfaceof the black matrix, the properties of the sub-pixel regions will not beadversely affected by the silylation treatment. Furthermore, thepossibility of color ink overflow and intermixing of color inks betweenadjacent sub-pixels can be effectively reduced. Besides, the inkjetprinting process can also economize the use of the silylate materials.

It should be noted that even though the above embodiments describe thefabrication process of a color filter, one of ordinary skill in the artmay well appreciate that the above method fabrication process may alsobe similarly applied in PLED (polymer light emitted diode) for modifyingthe property of the ITO layer, the well, the bank, or the hole throughlayer (HTL) etc.

In summary, the method of fabricating the color filter of the presentinvention including forming a hydrophobic layer over the surface of theblack matrix or performing a silylation treatment to clean the surfaceof the black matrix for substantially reducing the possibility ofintermixing of color ink between adjacent sub-pixel regions. Comparedwith the conventional art, the present invention provides a much saferand simpler process. Furthermore, the fabrication cost can beeffectively reduced, and the fabrication yield can be effectivelypromoted.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A method of fabricating a color filter, comprising: providing asubstrate having a light shielding layer disposed thereon, wherein thelight shielding layer is adopted for defining a plurality of sub-pixelregions on the substrate; performing a stencil printing process to forma hydrophobic layer on the light shielding layer; and forming a colorfilter layer in the sub-pixel regions.
 2. The method according to claim1, wherein the stencil printing process comprises: providing a stencilover the substrate for covering the sub-pixel regions such that thelight shielding layer is exposed; filling a liquid hydrophobic materialonto the exposed light shielding layer; solidifying the liquidhydrophobic material to form a solid hydrophobic layer; and removing thestencil.
 3. The method according to claim 1, wherein the hydrophobiclayer comprises paraffin.
 4. The method according to claim 1, furthercomprising removing the solid hydrophobic layer after forming the colorfilter layer.
 5. The method according to claim 4, wherein thehydrophobic layer is removed by using a solution.
 6. The methodaccording to claim 5, wherein the solution comprises ether.
 7. Themethod according to claim 1, wherein the color filter layer is formed byperforming an inkjet printing process or a photolithography process. 8.The method according to claim 1 wherein the light shielding layer is ablack matrix.
 9. The method according to claim 8, wherein the blackmatrix comprises epoxy resin.